Refrigeration appliance having a siphon in the condensate drain

ABSTRACT

A refrigeration appliance, particularly a domestic refrigeration appliance, has an inner chamber surrounded by a thermal barrier coating, an evaporator which cools the inner chamber, and a condensate drain which leads into the open from the evaporator through the thermal barrier coating. The condensate drain includes a siphon, which is arranged on the inner side of the thermal barrier coating and which is heatable by a defrost heater.

The present invention relates to a refrigeration appliance, inparticular a domestic refrigeration appliance, comprising an innercompartment surrounded by a thermal insulation layer, an evaporatorwhich cools the inner compartment, and a condensate drain which leadsinto the open from the evaporator through said thermal insulation layer.

If a condensate drain of this kind can be passed through freely duringoperation of the refrigeration appliance, then there is a constant airexchange with the surroundings via the condensate drain, and heat andmoisture find their way into the inner compartment via the condensatedrain in an undesirable manner. In order to prevent this, it is knownfrom DE 10 2008 040 430 A1 for example to provide a siphon in thecondensate drain which, by containing liquid water at all times, onlyallows air to pass between the inner compartment and the surroundingswhen a sufficiently large pressure difference is present between theinterior and exterior.

Such a siphon may, at least in a refrigeration appliance, the innercompartment of which reaches temperatures below 0 degrees Celsius, onlybe arranged outside the thermal insulation layer, since a freezing ofwater contained in the siphon would cause it to clog and render ituseless. Accommodating the siphon in the machine room is difficult,since it must neither block the cooling of the components present therenor heat up near said components to the extent that it dries up in ashort space of time and the air tightness of the siphon between twodefrost cycles is not ensured. Mounting the siphon onto a rear wall ofthe appliance is also problematic, since this requires either areduction in the size of the rear wall evaporator conventionallyprovided there, or the bringing forward of the thermal insulation layerof the rear wall and thus entails a considerable loss of usable volume.

The object of the invention is to specify a refrigeration appliance,which enables a simple and space-saving installation of a siphon in thecondensate drain.

The object is achieved for a refrigeration appliance, in particular adomestic refrigeration appliance comprising an inner compartmentsurrounded by a thermal insulation layer, an evaporator which cools theinner compartment and a condensate drain which leads into the open fromthe evaporator through said thermal insulation layer and has a siphon,by the siphon being arranged on the inner side of the thermal insulationlayer and being heatable by a defrost heater. In the inner compartment,the siphon should be accommodated relatively easily, without anassociated displacement of the thermal insulation layer and thus anoticeable loss of usable volume. The risk of the condensate drainbecoming air-permeable as a result of premature evaporation of the waterin the siphon is eliminated by the low temperature at which the siphonis kept. By guiding the condensate drain along a short, preferablystraight path through the thermal insulation layer, the weakening of theinsulating effect of the thermal insulation layer by the condensatedrain is limited to a minimum. As long as the water in the condensatedrain is frozen, there forms an immovable obstruction, which alsoprevents the occurrence of bubbling noises, which occur in a siphonfilled with liquid water when for example warm air, which has found itsway into the inner compartment of the refrigeration appliance when thedoor is opened, cools down therein and surrounding air is sucked in viathe siphon as a result.

The defrost heater of the siphon should be coupled to a defrost heaterfor the evaporator from a functional perspective, in order to ensurethat the siphon is permeable or becomes permeable at the right time,when the evaporator is defrosted and condensate is to be drainedtherefrom via the siphon.

It is conceivable to operate the heaters of the siphon and theevaporator in a staggered manner, in particular the heater of the siphoncan be brought into operation shortly before the start of a defrostprocess, in order to ensure that the contents of the siphon becomesliquid at the right time and thus the siphon is permeable when thecondensate begins to flow from the evaporator.

Since, in practice, the evaporator also requires a particular operatingtime for its defrost heater until the condensate begins to flow, bothheaters may also be controlled via a common switch and thus operatedsimultaneously; according to a preferred embodiment a common defrostheater may be provided for the evaporator and for the siphon.

If the inner compartment is divided into a storage chamber and anevaporator chamber, the siphon is preferably arranged on the base of adepression in the evaporator chamber.

The defrost heater may extend over the depression, in order to heat itover a wide area, in particular by radiation.

The defrost heater may extend between the evaporator and the depression,in order to emit heat downward to the depression and upward to theevaporator simultaneously.

The defrost heater may in particular be in the shape of a plate or rod.

In order for the defrost heater to be able to defrost the siphon in areasonably short time by radiation, its operating temperature must lieconsiderably above 0° C.; it may then also heat the evaporator byradiation.

The base of the depression should be sloping with respect to the siphon,on the one hand in order to collect the condensate at the siphon, on theother hand in order to be able to keep a high-lying part of the basefree from water or ice, so that during a defrosting it can storeradiation directly from the defrost heater lying above and transfer theradiant heat to the ice in the siphon.

To make the heat conducting process effective, the base of thedepression may be provided with an infrared-absorbing surface layer.

In order to ensure a rapid transmission of the stored heat to the ice,the base of the depression may further be at least partially metallic.

Expediently, the siphon is formed by a connector protruding above thebase of the depression and a cup put over the connector.

A lower edge of the cup should lie at most 2 mm below the upper edge ofthe connector, in order to limit the quantity of water which has to bedefrosted in order to make the siphon permeable.

In order to accelerate this defrosting, a surface of the siphon facingtoward the defrost heater, in particular a top side of the cup, may beprovided with an infrared-absorbing surface layer.

Further features and advantages of the invention will emerge from thedescription of exemplary embodiments provided below, with reference tothe attached figures, in which:

FIG. 1 shows a schematic cross-section through a domestic refrigerationappliance according to the invention;

FIG. 2 shows an enlarged extract from FIG. 1 in accordance with a firstembodiment;

FIG. 3 shows a similar cross-section to FIG. 2 in accordance with asecond embodiment; and

FIG. 4 shows a partial section through a refrigeration appliance inaccordance with a third embodiment of the invention.

FIG. 1 shows a schematic cross-section through a no-frost domesticrefrigeration appliance with a carcass 1 and a door 2, which are in eachcase foamed with a thermal insulation layer 3 and surround an innercompartment 4. The inner compartment 4 is divided by a dividing wall 5into a storage chamber 6 accessible via the door 2 and an evaporatorchamber 7, which extends with an upright orientation between thedividing wall 5 and a rear wall 8 of the carcass 1. The evaporatorchamber 7 is filled to a great extent by an evaporator 9, typically afin evaporator. A fan 10 is arranged in an opening of the dividing wall5, in order to drive air circulation between the storage chamber 6 andthe evaporator chamber 7 when the evaporator 9 is operating.

A horizontal or slightly forwardly inclined wall 11 of the carcass 1separates the evaporator chamber 7 from a machine room 12, which liesoutside the thermal insulation layer 3 and contains a compressor 13 etc.

An inner container deep-drawn from plastic separates the innercompartment 4 from the thermal insulation layer 3 in the conventionalmanner. A depression 14 is formed on the base of the evaporator chamber7 in the inner container, which extends over the entire width of theevaporator chamber 7. A siphon 15 at the deepest point of the depression14 forms the starting point of a condensate drain 16, which extendsvertically through the wall 11 to an evaporation pan 17 heated by thecompressor 13 in the machine room 12.

FIG. 2 shows the siphon 15 and its surroundings in an enlargedcross-section in accordance with a first embodiment of the invention.The siphon 15 comprises a cylindrical connector 18, which extends upwardfrom the base of the depression 14, as well as a pan or a cup 19, whichis put over the free end of the connector 18 upside down. In order tokeep a base 20 of the cup 19 at a distance from the upper edge 21 of theconnector 18, the surrounding wall 22 of the cup 19 may be provided withsmall individual feet 23, which are supported around the connector 18 onthe base of the depression 14, here in a trench 24 surrounding theconnector 18.

An electrical resistor heater 25 is attached to an outer side of thetrench 24 facing toward the thermal insulation layer 3 and can beoperated together with a resistance heater 26 attached to the finevaporator 9, in order to also defrost the water in the trench 24 duringa defrosting of the evaporator 9 at the right time in each case, so thata free draining of the defrost water from the evaporator 9 via thecondensate drain 16 to the evaporation pan 17 is ensured. Following theconclusion of the defrost process, the trench 24 remains filled withwater up to the upper edge 21 of the connector 18, so that as soon asthe evaporator 9 cools again, the water in the trench 24 freezes andseals the siphon 15 tightly.

FIG. 3 shows a schematic cross-section through the siphon 15 inaccordance with a preferred second embodiment of the invention. Here, aplate-shaped resistance heater 27 is arranged with a horizontalorientation over the depression 14 and below the fin evaporator 9. Inits place, a rod-shaped heater could also be provided and in particularcould be oriented in a straight line perpendicular to the cross-sectionplane or could run in a horizontal plane in a serpentine manner. Asecond heater could be arranged immediately on the fin evaporator 9 asin the heater 26 of FIG. 2 and be operated together with the resistanceheater 27 in order to heat the evaporator 9, when the resistance heater27 simultaneously heats the water in the siphon 15. In the embodimentshown in FIG. 3, infrared radiation emitted by the resistance heater 27heats both the fin evaporator 9 and also the siphon 15.

Infrared radiation emitted downward by the heater 27 is intercepted onthe one hand by the cup 19 and on the other by the base of thedepression 14. The cup 19 emits the heat which it has intercepted to thebody of ice 28 via the lower edge of the wall 22 submerged in the bodyof ice 28 surrounding the connector 18. So that defrost water flowing infrom the evaporator 9 is able to drain, the body of ice 28 must not becompletely defrosted. Rather, it is sufficient if the ice has beenliquefied continuously from the outside to the inside at one point alongthe circumference of the wall 22. The lower the vertical overlap dbetween the wall 22 and the connector 18, the smaller the quantity ofice immediately at the surface of the wall 2, to which the cup 19 emitsits heat and which has to be liquefied in order to make the siphon 15permeable.

In order to ensure a rapid draining of the defrost water, it is useful,however, if the body of ice 28 is completely defrosted straight away.The walls 29 of the depression 14 steeply sloping toward the siphon 15and the low height of the connector 18 ensure that at the end of eachdefrost process only a small part of the walls 29 around the connector18 is covered by water; the majority of the walls 29 which lies higherthan the upper edge 21 of the connector 18 therefore remains ice-freeduring the cooling operation and quickly heats up during the followingdefrost process due to the radiation of the heater 27. In order torapidly divert this heat to the body of ice 28, the walls 29 may becoated with a thin metal sheet 30 or a metal film; in order to renderthe absorption of the infrared radiation effective, the metal sheet 30and the cup 19 may in each case be provided with yet anotherinfrared-absorbing coating 31.

FIG. 4 shows as a third embodiment of the invention a schematiccross-section through a siphon 15 and the surroundings thereof in arefrigeration appliance with an evaporator chamber 7 arrangedhorizontally below a cover 32 of the carcass. Here, the heater 27extends below a width side of the fin evaporator 9 and can heat it bothby radiation and also by direct contact. Between a front region of theheater 27 and the wall 5 separating the evaporator chamber 7 from thestorage chamber 6, an infrared-reflecting film 33 is arranged in orderto minimize the heat emission to the wall 5 which lies below andseparates the evaporator chamber 7 from the storage chamber 6.

Film 33 and wall 5 are steeply inclined with respect to the rear wall 8,in order to guide defrost water draining from the evaporator 9 to thedepression 14, which is arranged here in a rear part of the wall 5. Arear region 34 of the heater 27 protruding out beyond the heater 27emits heat radiation downward, in order to heat the depression 14 andthe siphon 15—here constructed in the exact same manner as in theembodiment in FIG. 2.

REFERENCE CHARACTERS

-   1 Carcass-   2 Door-   3 Thermal insulation layer-   4 Inner compartment-   5 Dividing wall-   6 Storage chamber-   7 Evaporator chamber-   8 Rear wall-   9 Evaporator-   10 Fan-   11 Wall-   12 Machine room-   13 Compressor-   14 Depression-   15 Siphon-   16 Condensate drain-   17 Evaporation pan-   18 Connector-   19 Cup-   20 Base-   21 Upper edge-   22 Wall-   23 Small foot-   24 Trench-   25 Resistance heater-   26 Resistance heater-   27 Resistance heater-   28 Body of ice-   29 Wall-   30 Metal sheet-   31 Coating-   32 Cover-   33 Film-   34 Rear region

1-14. (canceled)
 15. A refrigeration appliance, comprising: a thermalinsulation layer surrounding an inner compartment; an evaporatorconfigured to cool said inner compartment; a condensate drain leadingfrom said evaporator through said thermal insulation layer and into theopen, said condensate drain including a siphon disposed on an inner sideof said thermal insulation layer; and a defrost heater configured forheating said siphon.
 16. The refrigeration appliance according to claim15, wherein said defrost heater of said siphon is functionally coupledto a further defrost heater for said evaporator.
 17. The refrigerationappliance according to claim 15, wherein said defrost heater is a commondefrost heater for said evaporator and for said siphon.
 18. Therefrigeration appliance according to claim 15, wherein said innercompartment is divided into a storage chamber and an evaporator chamber,said evaporator chamber is formed with a depression, and said siphon isarranged on a base of said depression formed in said evaporator chamber.19. The refrigeration appliance according to claim 18, wherein saiddefrost heater extends over said depression.
 20. The refrigerationappliance according to claim 18, wherein said defrost heater extendsbetween said evaporator and said depression.
 21. The refrigerationappliance according to claim 18, wherein said defrost heater isplate-shaped or rod-shaped.
 22. The refrigeration appliance according toclaim 18, wherein said evaporator chamber is arranged upright on a rearside of said inner compartment and said defrost heater is a radiationheater.
 23. The refrigeration appliance according to claim 18, whereinthe base of said depression is sloped towards said siphon.
 24. Therefrigeration appliance according to claim 18, comprising anIR-absorbing surface layer on the base of said depression.
 25. Therefrigeration appliance according to claim 18, wherein the base of saiddepression is at least partially metallic.
 26. The refrigerationappliance according to claim 18, wherein said siphon comprises aconnector protruding above the base of said depression and a cupdisposed on said connector.
 27. The refrigeration appliance according toclaim 26, wherein a lower edge of said cup lies at most 2 mm below anupper edge of said connector.
 28. The refrigeration appliance accordingto claim 15, comprising an IR-absorbing surface layer on a surface ofsaid siphon facing toward said defrost heater.
 29. The refrigerationappliance according to claim 15 configured as a domestic refrigerationappliance.